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Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

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Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#51

Post by prutschman »

X-Istence wrote: post #31
mankyd wrote: post #25

Earlier quoted context omitted.

Usually, when jumping another car, you are supposed to leave the car running, getting power off the alternator rather than the battery.

You don't get the massive amount of power required for the starter from the alternator. You leave your car on so that in case the other car is severely broken or zaps all the remaining juice in your car's battery you don't end up stranded.

You don't need to; I used to have a really crummy set of jumper cables that wouldn't actually pass enough power to start my car with the battery dead. I'd have to stay connected to the other car long enough to let its alternator charge my battery enough to start.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#52

Post by cmain »

Eiriksmal wrote: post #48
sokoloff wrote: post #28

> Oh, and its lifespan (7 years) is about twice that of a lead-acid battery (3-4 years). I live in Cambridge, MA (so we get winters) and I can't remember the last time I've had a regularly driven car's battery fail in under 7 years.

I've never figured out why some batteries last and others don't. My '05 6MT V6 sedan still had its OEM battery when the starter finally refused to turn over in 2013. My wife's '07 5AT I4 sedan just got its fourth battery this month. My car grew up in central Kentucky, hers spent its first 3 years in New England before also moving to ol' Kintuck.

Not that this was necessarily the case with your vehicles, but battery placement in a vehicle will directly affect its lifespan. If it's closer to a heat source (e.g. the engine), it will die much faster. This is why some manufacturers put them in the wheel well or the trunk.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#53

Post by [deleted] »

sandworm101 wrote: post #27

(1) Those nasty things inside car batteries are easily recycled and in fact are recycled more often than not (like 95%+) (2) Car batteries do not last only 3-4 years as per the OP. Car batteries can last decades. There are many variables, but the car in my battery is far older than 4 years. (lol) (3) Replacing an easily-recyclable product with a less-recyclable one is no step forwards. (4) XX addressed by OP comment,…

[deleted]

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#54

Post by blueintegral »

msandford wrote: post #17

How does it handle a car that's iffy on starting? It's probably not hard to get something that'll crank a starter for a few seconds. But what happens if it needs to crank for 60 seconds over a 90 second window? I've got a 2006 Forester with a manual. I'll occasionally stall it backing out of a parking spot, so I'll have to start it again. For some reason it's much more difficult to start in between cold and warmed up…

It's hard for me to say exactly how many times you can start it before having to wait for the caps to charge back up, since we've measured a surprisingly high variation of required starting current over a bunch of different cars. One of our testers drives a Datsun 240z (it's really sweet) and sometimes needs a few cranks to get it going. He hasn't had to change his behavior from his old battery, so he's getting at least a few attempts over a short period without needing to wait for recharging. One other cool trick we can do is charge the capacitors slightly higher to deliver more current on a second starting attempt, which will hopefully reduce the number of cranking attempts you need.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#55

Post by Sanddancer »

tomkinstinch wrote: post #26
Sanddancer wrote: post #20

Earlier quoted context omitted.

A lot of hybrids, like the Prius [1] have a second battery designed for turning over the engine that are designed for different usage cases than the drivetrain batteries; it's also why this battery has a supercapacitor for starting, and lithium polymers for the rest of the time. Additionally, there are a lot of people who like older cars, think hotrodders, etc, where a battery like this would also be useful. It's def…

Slight correction as a Gen II Prius driver: In the Prius, the 12V battery only runs the control electronics of the car (and a few small motors like the wipers); the engine is turned over by a high-voltage motor running from the main "traction" battery. The smaller 12V battery is charged from the high-voltage battery which is itself charged from the gasoline engine via the hybrid transmission. All that is to say that…

Thanks. Should have known not to trust a battery vendor's page touting its superior cold cranking amps for a hybrid. Though for the hybrid battery pack, you'd want to stick with more traditional batteries. Supercapacitors are better when you need to provide a lot of current at once, but they don't have nearly the energy density of lithium, or even lead, batteries.

It is possible, though, that a supercapacitor bank could be useful in the frontend to serve much like this battery does. I could see it being potentially useful to have the supercapacitor get the motors turning to provide torque as fast as possible, with the regular batteries providing the lower current to keep things going.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#56

Post by conjecTech »

jasonlaramburu wrote: post #3

Great idea in a very stagnant market. How do the LiFePO4 cells perform at high temperatures? I've worked with this battery chemistry before, and found most off the shelf cells have internal safety circuitry that disconnects the battery at temperatures >70C. Typical engine running temperature is 60-80C (or as much as 90 on a hot day).

Hey Jason, good question. It turns out to be a non-issue. Lead-acid batteries have terrible lifetimes at high temperatures, so cars are already designed with enough distance between the engine and battery and enough circulation to ensure the battery is never more than a few degrees above ambient. The batteries in our design also aren't generally active while the engine is running. Let me know if that addresses your concerns.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#57

Post by blueintegral »

shabble wrote: post #38
devicenull wrote: post #18

Earlier quoted context omitted.

> if it’s ever about to reach the point that it’ll no longer be able to start your car, it’ll just turn itself off. Your lights will fade out and the radio will go quiet — but once you turn the key, everything will spring right back to life, no jump start required. How does that work? If the battery stops providing current to prevent itself from being fully drained, you're not going to have power to the car's compute…

One possibility: It will know when the internal batteries are running low (the internal charge/discharge monitor IC doing battery "gas gauge" measuring). It'll maintain a reserve of a few crank's worth of energy, and trigger shutdown before that's exhausted. It can also tell if the engine is running, because the alternator will be, and charging it. It can also monitor the active discharge current. If the battery is l…

Bingo.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#58

Post by CamperBob2 »

blueintegral wrote: post #50
sandworm101 wrote: post #27

(1) Those nasty things inside car batteries are easily recycled and in fact are recycled more often than not (like 95%+) (2) Car batteries do not last only 3-4 years as per the OP. Car batteries can last decades. There are many variables, but the car in my battery is far older than 4 years. (lol) (3) Replacing an easily-recyclable product with a less-recyclable one is no step forwards. (4) XX addressed by OP comment,…

You're right! Lead acid car batteries are one of the great recycling success stories. What's interesting is that the volume of lead acid car batteries in the world is so high, that even at that high recycling rate, that still leaves 24 million pounds of lead each year from car batteries that don't get recycled. There's also been some problems recently with lead recycling plants contaminating the environment [1]. You'…

Some thoughts:

The price point is impressive if you can sell at only ~$50 more than a standard lead-acid battery. If pressed to find a flaw, I think the biggest is one you've already identified:

   There’s one: you can’t run your lights and/or stereo as 
   long with your engine turned off. Ohm’s battery reserve 
   comes in at 10 amp hours; most lead-acid car batteries 
   come in at about 45 amp hours. If you can run your 
   stereo with your engine off for three hours on your 
   current battery, you’d be able to run it on Ohm for less 
   than an hour.
Nobody with a modern car or SUV is going to get three hours' runtime for their accessory equipment. With the original equipment (AGM lead acid, 70 AH/450 CCA) battery in my two-seat passenger car, I'm lucky to get 15 minutes' worth of stereo/nav/etc. operation with the ignition off. There's no conceivable way that 10 AH is enough for this application. The more "luxurious" the car, and the newer it is, the worse this problem will be. Meanwhile, LiFePO4 battery cost will probably go in the opposite direction, leaving room for competitors to offer more power for less money.

So I'd reconsider the size of the LiFePO4 battery, even if it makes the product cost a bit more. You need those high-end buyers. You're not going to sell these to Joe Sixpack for installation in his '98 F-150 pickup.

And yes, your marketing materials are grossly exaggerating both the environmental problems with lead-acid batteries and their typical service life. There is clearly a global regulatory jihad against lead in all of its forms and uses, though, so you do have that going for you.

Edit: Don't forget that auto stop/start is growing in popularity as well. I think it's actually mandatory in some (European?) markets. OEMs are moving toward "smarter" (read: DRM-locked) batteries to handle these additional requirements. I wonder if a better business model might be to offer recycling/rebuilding services that swap out lead plates for LiFePO4/supercap hardware in existing batteries?

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#59

Post by blueintegral »

daniel-levin wrote: post #10
blueintegral wrote: post #2

Hey everyone! I'm Hunter, one of the cofounders of Ohm. Let me know if I can answer any questions.

Hi Hunter How much safety testing have you done on your battery? Specifically, if an Ohm battery is involved in a collision, how will it fare? I know you are not content with shipping anything you aren't comfortable with your own family members driving with [1]. But, how do you know this? What makes you so sure? I don't mean to come across as interrogative - I am just curious. [1] http://www.getohm.com/ edit: grammar

Yeah, safety is obviously the most important thing. Right now we're basing the safety claims on the those of the component manufacturers. But it's also going to be a function of the enclosure and component locations, etc. Once all of that is finalized, we'll have a 3rd party lab do abuse testing, crush testing, etc to make sure there aren't any bad failure modes. There's lots of good processes and test procedures already out there for doing that kind of testing on batteries.

Re: Ohm (YC S15) is a smarter, lighter car battery that works with your existing car

#60

Post by conjecTech »

mkarr wrote: post #16
blueintegral wrote: post #2

Hey everyone! I'm Hunter, one of the cofounders of Ohm. Let me know if I can answer any questions.

Hi Hunter. Do you all plan to offer the battery in a minimal form factor (without the group 35 adapter)? I currently am running one of the Shorai LiFePo4 batteries in my track car. I really love the small size and weight, and would be willing to work around the smaller form factor.

Yes, it will be available in a smaller form factor. The core of the device will be a single modular design that will be inserted in the shell shown to give it the Group 35 size. Thanks for the kind words!
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